The high integration or high-density packaging of each component for semiconductor packages has been increasingly accelerated in recent years as semiconductor packages widely used in electronics, communication devices, personal computers, etc. have been more highly functionalized or miniaturized. Along with this, the difference in the coefficient of thermal expansion between a semiconductor device and a printed circuit board for semiconductor plastic packages causes the undesired warpage of semiconductor plastic packages. Various measures against this problem have been attempted.
One example of the measures includes reduction in thermal expansion of insulating layers for use in printed circuit boards. This approach is to suppress the warpage by bringing the coefficient of thermal expansion of a printed circuit board closer to the coefficient of thermal expansion of a semiconductor device and is currently being actively tackled (see e.g., Patent Documents 1 to 3).
In addition to the reduction in thermal expansion of printed circuit boards, increase in the rigidity of laminates (high rigidity) or increase in the glass transition temperatures of laminates (high Tg) has been studied as an approach for suppressing the warpage of semiconductor plastic packages (see e.g., Patent Documents 4 and 5).